Coating architecture for plasma sprayed chamber components

ABSTRACT

A method of plasma spraying an article comprises inserting the article into a vacuum chamber for a low pressure plasma spraying system. A low pressure plasma spray process is then performed by the low pressure plasma spraying system to form a first plasma resistant layer having a thickness of 20-500 microns and a porosity of over 1%. A plasma spray thin film, plasma spray chemical vapor deposition or plasma spray physical vapor deposition process is then performed by the low pressure plasma spraying system to deposit a second plasma resistant layer on the first plasma resistant layer, the second plasma resistant layer having a thickness of less than 50 microns and a porosity of less than 1%.

RELATED APPLICATIONS

This patent application is a divisional application of U.S. patent application Ser. No. 14/462,057, filed Aug. 18, 2014, which claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/879,549, filed Sep. 18, 2013. Patent application Ser. No. 14/462,057 is incorporated by reference herein.

TECHNICAL FIELD

Embodiments of the present disclosure relate, in general, to ceramic coated articles and to a process for plasma spraying a ceramic coating onto chamber components.

BACKGROUND

In the semiconductor industry, devices are fabricated by a number of manufacturing processes producing structures of an ever-decreasing size. Some manufacturing processes such as plasma etch and plasma clean processes expose a substrate to a high-speed stream of plasma to etch or clean the substrate. The plasma may be highly corrosive, and may corrode processing chambers and other surfaces that are exposed to the plasma. This corrosion may generate particles, which frequently contaminate the substrate that is being processed, contributing to device defects.

As device geometries shrink, susceptibility to defects increases, and particle contaminant requirements become more stringent. Accordingly, as device geometries shrink, allowable levels of particle contamination may be reduced. To minimize particle contamination introduced by plasma etch and/or plasma clean processes, chamber materials have been developed that are resistant to plasmas. Different materials provide different material properties, such as plasma resistance, rigidity, flexural strength, thermal shock resistance, and so on. Also, different materials have different material costs. Accordingly, some materials have superior plasma resistance, other materials have lower costs, and still other materials have superior flexural strength and/or thermal shock resistance.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that different references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one.

FIG. 1 depicts a sectional view of one embodiment of a processing chamber.

FIG. 2 illustrates an exemplary architecture of a manufacturing system, in accordance with one embodiment of the present invention.

FIGS. 3-4 depict schematics of a plasma spray deposition system.

FIG. 5 illustrates one embodiment of a process for forming multiple plasma sprayed ceramic coating over a chamber component.

FIGS. 6-7 illustrate cross sectional side views of articles covered by one or more plasma sprayed protective layers.

DETAILED DESCRIPTION OF EMBODIMENTS

Some embodiments of the disclosure are directed to a process for forming a plasma resistant ceramic coating having a stack of at least two protective layers on an article. The at least two protective layers may have different thicknesses and/or densities and are deposited using different plasma spray processes. The processes disclosed herein provide improved plasma resistance performance for chamber components.

In one embodiment, an article (e.g., a chamber component) is inserted into a low pressure plasma spray chamber. A low pressure plasma spray process is performed by a plasma spraying system to form a first plasma resistant layer having a thickness of 100-200 microns and a porosity of over 1%. The plasma spraying system then performs a plasma spray thin film (PSTF), plasma spray physical vapor deposition (PSPVD) or plasma spray chemical vapor deposition (PSCVD) process to deposit a second plasma resistant layer on the first plasma resistant layer, the second plasma resistant layer having a thickness of 1-50 microns and a porosity of less than 1%. The PSTF, PSCVD or PSPVD plasma spray process may be performed by the same low pressure plasma spray chamber that performs the low pressure plasma spray process. Additionally, the PSTF, PSCVD or PSPVD plasma spray process may be performed immediately after the low pressure plasma spray process as part of a single deposition recipe. Alternatively, the first plasma spray process may be an atmospheric pressure plasma spray (APPS) process (also referred to as an air plasma spray (APS) process. In such an embodiment, the article would be placed into a low pressure plasma spray chamber to perform the PSTF, PSCVD or PSPVD process after performing the APPS process.

The ceramic coating of the article may be highly resistant to plasma etching, and the article may have superior mechanical properties such as a high flexural strength and a high thermal shock resistance. Performance properties of the coated ceramic article may include a high thermal capability, a long lifespan, and a low on-wafer particle and metal contamination. Additionally, by performing both the low pressure plasma spray process and the PSTF, PSCVD or PSPVD plasma spray processes in the same low pressure plasma spray chamber, cycle time and cost may be reduced.

When the terms “about” and “approximately” are used herein, these are intended to mean that the nominal value presented is precise within ±30%. The articles described herein may be structures that are exposed to plasma, such as chamber components for a plasma etcher (also known as a plasma etch reactor). For example, the articles may be walls, bases, gas distribution plates, rings, view ports, lids, nozzles, shower heads, substrate holding frames, electrostatic chucks (ESCs), face plates, selectivity modulation devices (SMDs), etc. of a plasma etcher, a plasma cleaner, a plasma propulsion system, and so forth.

Moreover, embodiments are described herein with reference to ceramic coated chamber components and other articles that may cause reduced particle contamination when used in a process chamber for plasma rich processes. However, it should be understood that the ceramic coated articles discussed herein may also provide reduced particle contamination when used in process chambers for other processes such as non-plasma etchers, non-plasma cleaners, chemical vapor deposition (CVD) chambers, physical vapor deposition (PVD) chambers, and so forth. Moreover, some embodiments are described with reference to specific plasma resistant ceramics. However, it should be understood that embodiments equally apply to other plasma resistant ceramics than those discussed herein.

FIG. 1 is a sectional view of a processing chamber 100 (e.g., a semiconductor processing chamber) having one or more chamber components that are coated with a ceramic coating in accordance with embodiments of the present invention. The processing chamber 100 may be used for processes in which a corrosive plasma environment is provided. For example, the processing chamber 100 may be a chamber for a plasma etch reactor (also known as a plasma etcher), a plasma cleaner, and so forth. Examples of chamber components that may include a plasma resistant ceramic coating include a substrate support assembly 148, an electrostatic chuck (ESC) 150, a ring (e.g., a process kit ring or single ring), a chamber wall, a base, a gas distribution plate, a showerhead, a liner, a liner kit, a shield, a plasma screen, a flow equalizer, a cooling base, a chamber viewport, a chamber lid, a nozzle, process kit rings, and so on.

In one embodiment, the plasma resistant ceramic coating, which is described in greater detail below, is a multi-layer rare earth oxide coating deposited by a combination of a low pressure plasma spraying (LPPS) process and one of a plasma spray thin film (PSTF) process, a plasma spray chemical vapor deposition (PSCVD) process or a plasma spray physical vapor deposition (PSPVD) process. Alternatively, the plasma resistant ceramic coating may be a multi-layer rare earth oxide coating deposited by a combination of an atmospheric pressure plasma spray (APPS) process and one of a PSTF, PSCVD or PSPVD process.

The plasma resistant ceramic coating may have multiple plasma resistant layers, in accordance with embodiments. The multiple layers may each have the same material composition or may have different material compositions. Any of the layers of the plasma resistant coating may include Y₂O₃ and Y₂O₃ based ceramics, Y₃Al₅O₁₂ (YAG), Al₂O₃ (alumina), Y₄Al₂O₉ (YAM), SiC (silicon carbide) Si₃N₄ (silicon nitride), SiN (silicon nitride), MN (aluminum nitride), TiO₂ (titania), ZrO₂ (zirconia), TiC (titanium carbide), ZrC (zirconium carbide), TiN (titanium nitride), Y₂O₃ stabilized ZrO₂ (YSZ), Er₂O₃ and Er₂O₃ based ceramics, Gd₂O₃ and Gd₂O₃ based ceramics, Er₃Al₅O₁₂ (EAG), Gd₃Al₅O₁₂ (GAG), Nd₂O₃ and Nd₂O₃ based ceramics, and/or a ceramic compound comprising Y₄Al₂O₉ and a solid-solution of Y₂O₃—ZrO₂.

Any of the layers of the plasma resistant ceramic coating may also be based on a solid solution formed by any of the aforementioned ceramics. With reference to the ceramic compound comprising Y₄Al₂O₉ and a solid-solution of Y₂O₃—ZrO₂, in one embodiment the ceramic compound includes 62.93 molar ratio (mol %) Y₂O₃, 23.23 mol % ZrO₂ and 13.94 mol % Al₂O₃. In another embodiment, the ceramic compound can include Y₂O₃ in a range of 50-75 mol %, ZrO₂ in a range of 10-30 mol % and Al₂O₃ in a range of 10-30 mol %. In another embodiment, the ceramic compound can include Y₂O₃ in a range of 40-100 mol %, ZrO₂ in a range of 0-60 mol % and Al₂O₃ in a range of 0-10 mol %. In another embodiment, the ceramic compound can include Y₂O₃ in a range of 40-60 mol %, ZrO₂ in a range of 30-50 mol % and Al₂O₃ in a range of 10-20 mol %. In another embodiment, the ceramic compound can include Y₂O₃ in a range of 40-50 mol %, ZrO₂ in a range of 20-40 mol % and Al₂O₃ in a range of 20-40 mol %. In another embodiment, the ceramic compound can include Y₂O₃ in a range of 70-90 mol %, ZrO₂ in a range of 0-20 mol % and Al₂O₃ in a range of 10-20 mol %. In another embodiment, the ceramic compound can include Y₂O₃ in a range of 60-80 mol %, ZrO₂ in a range of 0-10 mol % and Al₂O₃ in a range of 20-40 mol %. In another embodiment, the ceramic compound can include Y₂O₃ in a range of 40-60 mol %, ZrO₂ in a range of 0-20 mol % and Al₂O₃ in a range of 30-40 mol %. In other embodiments, other distributions may also be used for the ceramic compound.

In one embodiment, an alternative ceramic compound that includes a combination of Y₂O₃, ZrO₂, Er₂O₃, Gd₂O₃ and SiO₂ is used for one or more layers of the plasma resistant ceramic coating. In one embodiment, the alternative ceramic compound can include Y₂O₃ in a range of 40-45 mol %, ZrO₂ in a range of 0-10 mol %, Er2O3 in a range of 35-40 mol %, Gd₂O₃ in a range of 5-10 mol % and SiO2 in a range of 5-15 mol %. In a first example, the alternative ceramic compound includes 40 mol % Y₂O₃, 5 mol % ZrO₂, 35 mol % Er₂O₃, 5 mol % Gd₂O₃ and 15 mol % SiO₂. In a second example, the alternative ceramic compound includes 45 mol % Y₂O₃, 5 mol % ZrO₂, 35 mol % Er₂O₃, 10 mol % Gd₂O₃ and 5 mol % SiO₂. In a third example, the alternative ceramic compound includes 40 mol % Y₂O₃, 5 mol % ZrO₂, 40 mol % Er₂O₃, 7 mol % Gd₂O₃ and 8 mol % SiO₂.

Any of the aforementioned plasma resistant ceramic coatings may include trace amounts of other materials such as ZrO₂, Al₂O₃, SiO₂, B₂O₃, Er₂O₃, Nd₂O₃, Nb₂O₅, CeO₂, Sm₂O₃, Yb₂O₃, or other oxides. The ceramic coating allows for longer working lifetimes due to the plasma resistance of the ceramic coating and decreased on-wafer or substrate contamination. Beneficially, in some embodiments the ceramic coating may be stripped and re-coated without affecting the dimensions of the substrates that are coated.

In one embodiment, the processing chamber 100 includes a chamber body 102 and a lid 130 that enclose an interior volume 106. The lid 130 may have a hole in its center, and a nozzle 132 may be inserted into the hole. The chamber body 102 may be fabricated from aluminum, stainless steel or other suitable material. The chamber body 102 generally includes sidewalls 108 and a bottom 110. Sidewalls 108 and/or bottom 110 may include a plasma resistant ceramic coating.

An outer liner 116 may be disposed adjacent the sidewalls 108 to protect the chamber body 102. The outer liner 116 may be fabricated and/or coated with a plasma resistant ceramic coating. In one embodiment, the outer liner 116 is fabricated from aluminum oxide.

An exhaust port 126 may be defined in the chamber body 102, and may couple the interior volume 106 to a pump system 128. The pump system 128 may include one or more pumps and throttle valves utilized to evacuate and regulate the pressure of the interior volume 106 of the processing chamber 100.

The lid 130 may be supported on the sidewall 108 of the chamber body 102. The lid 130 may be opened to allow access to the interior volume 106 of the processing chamber 100, and may provide a seal for the processing chamber 100 while closed. A gas panel 158 may be coupled to the processing chamber 100 to provide process and/or cleaning gases to the interior volume 106 through the nozzle 132. The lid 130 may be a ceramic such as Al₂O₃, Y₂O₃, YAG, SiO₂, AlN, SiN, SiC, Si—SiC, or a ceramic compound comprising Y₄Al₂O₉ and a solid-solution of Y₂O₃—ZrO₂. The nozzle 132 may also be a ceramic, such as any of those ceramics mentioned for the lid. The lid 130 may include a plasma resistant ceramic coating 133. The nozzle 132 may be coated with a plasma resistant ceramic coating 134.

Examples of processing gases that may be used to process substrates in the processing chamber 100 include halogen-containing gases, such as C₂F₆, SF₆, SiCl₄, HBr, NF₃, CF₄, CHF₃, CH₂F₃, F, NF₃, Cl₂, CCl₄, BCl₃ and SiF₄, among others, and other gases such as O₂, or N₂O. Examples of carrier gases include N₂, He, Ar, and other gases inert to process gases (e.g., non-reactive gases). A substrate support assembly 148 is disposed in the interior volume 106 of the processing chamber 100 below the lid 130. The substrate support assembly 148 holds a substrate 144 during processing. A ring 146 (e.g., a single ring) may cover a portion of the electrostatic chuck 150, and may protect the covered portion from exposure to plasma during processing. The ring 146 may be silicon or quartz in one embodiment. The ring 146 may include a plasma resistant ceramic coating.

An inner liner 118 may be coated on the periphery of the substrate support assembly 148. The inner liner 118 may be a halogen-containing gas resist material such as those discussed with reference to the outer liner 116. In one embodiment, the inner liner 118 may be fabricated from the same materials of the outer liner 116. Additionally, the inner liner 118 may be coated with a plasma resistant ceramic coating.

In one embodiment, the substrate support assembly 148 includes a mounting plate 162 supporting a pedestal 152, and an electrostatic chuck 150. The electrostatic chuck 150 further includes a thermally conductive base 164 and an electrostatic puck 166 bonded to the thermally conductive base by a bond 138, which may be a silicone bond in one embodiment. The mounting plate 162 is coupled to the bottom 110 of the chamber body 102 and includes passages for routing utilities (e.g., fluids, power lines, sensor leads, etc.) to the thermally conductive base 164 and the electrostatic puck 166.

The electrostatic puck 166 may include a plasma resistant ceramic coating. The thermally conductive base 164 and/or electrostatic puck 166 may include one or more optional embedded heating elements 176, embedded thermal isolators 174 and/or conduits 168, 170 to control a lateral temperature profile of the substrate support assembly 148. The conduits 168, 170 may be fluidly coupled to a fluid source 172 that circulates a temperature regulating fluid through the conduits 168, 170. The embedded isolators 174 may be disposed between the conduits 168, 170 in one embodiment. The optional embedded heating elements 176 is regulated by a heater power source 178. The conduits 168, 170 and optional embedded heating elements 176 may be utilized to control the temperature of the thermally conductive base 164, thereby heating and/or cooling the electrostatic puck 166 and a substrate (e.g., a wafer) 144 being processed. The temperature of the electrostatic puck 166 and the thermally conductive base 164 may be monitored using a plurality of temperature sensors 190, 192, which may be monitored using a controller 195.

The electrostatic puck 166 may further include multiple gas passages such as grooves, mesas and other surface features that may be formed in an upper surface of the electrostatic puck 166. The gas passages may be fluidly coupled to a source of a heat transfer (or backside) gas such as He via holes drilled in the electrostatic puck 166. In operation, the backside gas may be provided at controlled pressure into the gas passages to enhance the heat transfer between the electrostatic puck 166 and the substrate 144.

The electrostatic puck 166 includes at least one clamping electrode 180 controlled by a chucking power source 182. The at least one clamping electrode 180 (or other electrode disposed in the electrostatic puck 166 or thermally conductive base 164) may further be coupled to one or more RF power sources 184, 186 through a matching circuit 188 for maintaining a plasma formed from process and/or other gases within the processing chamber 100. The one or more RF power sources 184, 186 are generally capable of producing RF signal having a frequency from about 50 kHz to about 3 GHz and a power of up to about 10,000 Watts.

FIG. 2 illustrates an exemplary architecture of a manufacturing system 200. The manufacturing system 200 may be a ceramics manufacturing system. In one embodiment, the manufacturing system 200 includes manufacturing machines 201 (e.g., processing equipment) connected to an equipment automation layer 215. The manufacturing machines 201 may include a bead blaster 202, one or more wet cleaners 203, and/or a plasma spraying system 204. The manufacturing system 200 may further include one or more computing device 220 connected to the equipment automation layer 215. In alternative embodiments, the manufacturing system 200 may include more or fewer components. For example, the manufacturing system 200 may include manually operated (e.g., off-line) manufacturing machines 201 without the equipment automation layer 215 or the computing device 220.

Bead blaster 202 is a machine configured to roughen the surface of articles such as articles. Bead blaster 202 may be a bead blasting cabinet, a hand held bead blaster, or other type of bead blaster. Bead blaster 202 may roughen a substrate by bombarding the substrate with beads or particles. In one embodiment, bead blaster 202 fires ceramic beads or particles at the substrate. The roughness achieved by the bead blaster 202 may be based on a force used to fire the beads, bead materials, bead sizes, distance of the bead blaster from the substrate, processing duration, and so forth. In one embodiment, the bead blaster uses a range of bead sizes to roughen the ceramic article.

In alternative embodiments, other types of surface rougheners than a bead blaster 202 may be used. For example, a motorized abrasive pad may be used to roughen the surface of ceramic substrates. A sander may rotate or vibrate the abrasive pad while the abrasive pad is pressed against a surface of the article. A roughness achieved by the abrasive pad may depend on an applied pressure, on a vibration or rotation rate and/or on a roughness of the abrasive pad.

Wet cleaners 203 are cleaning apparatuses that clean articles (e.g., articles) using a wet clean process. Wet cleaners 203 include wet baths filled with liquids, in which the substrate is immersed to clean the substrate. Wet cleaners 203 may agitate the wet bath using ultrasonic waves during cleaning to improve a cleaning efficacy. This is referred to herein as sonicating the wet bath.

In other embodiments, alternative types of cleaners such as dry cleaners may be used to clean the articles. Dry cleaners may clean articles by applying heat, by applying gas, by applying plasma, and so forth.

Plasma spraying system 204 is a machine configured to plasma spray a ceramic coating to the surface of a substrate. Plasma spraying systems are discussed in greater detail with reference to FIGS. 3-4.

The equipment automation layer 215 may interconnect some or all of the manufacturing machines 201 with computing devices 220, with other manufacturing machines, with metrology tools and/or other devices. The equipment automation layer 215 may include a network (e.g., a location area network (LAN)), routers, gateways, servers, data stores, and so on. Manufacturing machines 201 may connect to the equipment automation layer 215 via a SEMI Equipment Communications Standard/Generic Equipment Model (SECS/GEM) interface, via an Ethernet interface, and/or via other interfaces. In one embodiment, the equipment automation layer 215 enables process data (e.g., data collected by manufacturing machines 201 during a process run) to be stored in a data store (not shown). In an alternative embodiment, the computing device 220 connects directly to one or more of the manufacturing machines 201.

In one embodiment, some or all manufacturing machines 201 include a programmable controller that can load, store and execute process recipes. The programmable controller may control temperature settings, gas and/or vacuum settings, time settings, etc. of manufacturing machines 201. The programmable controller may include a main memory (e.g., read-only memory (ROM), flash memory, dynamic random access memory (DRAM), static random access memory (SRAM), etc.), and/or a secondary memory (e.g., a data storage device such as a disk drive). The main memory and/or secondary memory may store instructions for performing heat treatment processes described herein.

The programmable controller may also include a processing device coupled to the main memory and/or secondary memory (e.g., via a bus) to execute the instructions. The processing device may be a general-purpose processing device such as a microprocessor, central processing unit, or the like. The processing device may also be a special-purpose processing device such as an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), network processor, or the like. In one embodiment, programmable controller is a programmable logic controller (PLC).

In one embodiment, the manufacturing machines 201 are programmed to execute recipes that will cause the manufacturing machines to roughen a substrate, clean a substrate and/or article, coat a article and/or machine (e.g., grind or polish) a article. In one embodiment, the manufacturing machines 201 are programmed to execute recipes that perform operations of a multi-step process for manufacturing a ceramic coated article, as described with reference to FIG. 5. The computing device 220 may store one or more ceramic coating recipes 225 that can be downloaded to the manufacturing machines 201 to cause the manufacturing machines 201 to manufacture ceramic coated articles in accordance with embodiments of the present disclosure.

FIGS. 3-4 illustrate an LPPS system 300 for plasma spraying a multi-layer plasma resistant ceramic coating on a chamber component or other article used in a corrosive system. The LPPS system 300 is a plasma spray system that includes a vacuum chamber 301 that can be pumped down to reduced pressure (e.g., to a vacuum of 1 Mbar, 10 Mbar, 35 Mbar, etc.). The LPPS system 300 may perform LPPS processes, PSPVD processes, PSCVD processes and/or PSTF processes.

In one embodiment (as illustrated), the LPPS system 300 is used to deposit a porous, low density first protective layer 312 and a thinner dense second protective layer 313 over the first protective layer 312. In an alternative embodiment, a conventional atmospheric pressure plasma spray (APPS) system that operates at atmospheric pressure is used to deposit the porous, low density first protective layer 312, and the LPPS 300 is used to deposit the thinner dense second protective layer 313 over the first protective layer 312. An APPS system does not include any vacuum chamber, and may instead include an open chamber or room.

In a plasma spray system, an arc is formed between two electrodes through which a gas is flowing. Examples of gas suitable for use in the low pressure plasma spray system 300 include, but are not limited to, Argon/Hydrogen or Argon/Helium. As the gas is heated by the arc, the gas expands and is accelerated through a shaped nozzle of a plasma torch 304, creating a high velocity plasma jet 302.

FIG. 3 shows deposition of the first protective layer 312 by the LPPS system 300 using an LPPS process. Powder 309 composed of a ceramic and/or metal material is injected into the plasma jet 302 by a powder delivery system 308. An intense temperature of the plasma jet 302 melts the powder 309 and propels the molten ceramic and/or metal material towards an article 310. Upon impacting with the article 310, the molten powder flattens, rapidly solidifies, and forms a first protective layer 312 of a ceramic coating. The molten powder adheres to the article 310. The parameters that affect the thickness, density, and roughness of the first protective layer 312 of the ceramic coating include type of powder, powder size distribution, powder feed rate, plasma gas composition, gas flow rate, energy input, pressure, and torch offset distance. In one embodiment, the LPPS system 300 performs an LPPS process to form the first protective layer 312 having a thickness of up to 50 microns. In another embodiment, the first protective layer 312 formed by the LPPS process has a thickness of up to 500 microns.

For LPPS processes, a chamber pressure of around 20-200 mbar may be used to produce coatings on the order of 20-500 microns. LPPS typically has a high velocity plasma jet flow. For LPPS, thermal energy of the plasma gas is converted to kinetic energy by the expansion of volume in the low pressure environment. LPPS processes may produce ceramic coatings with a porosity of about 1-5%. For LPPS, metallurgical bonding or diffusion bonding is a dominant bonding mechanism.

In one embodiment, the first protective layer 312 is formed by an APPS system performing an APPS process. In one embodiment, the first protective layer 312 formed by the APPS process has a thickness of approximately 20-500 microns. Alternatively, the first protective layer 312 may have other thicknesses. An APPS process may produce ceramic coatings having thicknesses of around 20 microns to several millimeters. The APPS process produces an oxide ceramic coating having a relatively high porosity. For example, APPS processes may produce ceramic coatings with a porosity of 1-5% in some embodiments. In some embodiments, APPS may produce ceramic coatings with a porosity of up to about 10%. For APPS, the ceramic coating bonds to the substrate mainly by mechanical bonding. As compared to LPPS, APPS typically has a lower velocity plasma jet flow with a higher temperature.

FIG. 4 shows deposition of the second protective layer 313 by the LPPS system 300 using one of a PSPVD, PSTF or PSCVD process. Feedstock 320 composed of a ceramic and/or metal material is injected into the plasma jet 302 by a feedstock delivery system 315. For PSPVD and PSTF processes, the feedstock is a powder composed of a ceramic and/or metal material. Accordingly, if a PSPVD process or PSTF process are to be performed, then feedstock 320 may correspond to powder 309 and feedstock delivery system 315 may correspond to powder delivery system 308. Moreover, if the second protective layer 313 is to have the same material composition of the first protective layer 312, then the same powder 309 may be used to perform both the first protective layer 312 and the second protective layer 313. For PSCVD processes, the feedstock is a liquid or vapor. Accordingly, if a PSCVD process is to be performed, then a different feedstock is used for the second protective layer 313 and the first protective layer 312, even if the two protective layers are to have the same material composition.

For PSCVD, PSTF and PSPVD processes, an intense temperature of the plasma jet 302 melts or vaporizes the feedstock 320 and propels the molten or vapor ceramic and/or metal material towards article 310. Upon impacting with the first protective layer 312, the molten powder flattens, rapidly solidifies, and forms a first protective layer 312 of a ceramic coating. Alternatively, upon impacting the first protective layer 312 the vaporized powder changes phase to a solid and forms the second protective layer 313 of the ceramic coating. The molten or vaporized powder adheres to the first protective layer 312. The parameters that affect the thickness, density, and roughness of the second protective layer 313 of the ceramic coating include type of feedstock, powder size distribution (if the feedstock is a powder), a feed rate, plasma gas composition, gas flow rate for the plasma, energy input, pressure, and torch offset distance.

In one embodiment, the LPPS system 300 performs a PSPVD process to form the second protective layer 313 having a thickness of 10-100 microns. PSPVD refers to a plasma spray process in which powder feedstock is typically vaporized and deposition occurs primarily from the vapor phase. Alternatively, PSPVD may melt powder feedstock to produce liquid splats that build up to form the second protective layer 313. For PSPVD processes, a chamber pressure of around 0.1-50 mbar may be used to produce dense coatings using high gun enthalpy to vaporize or melt ceramic feedstock material. The ceramic coatings produced by PSPVD have a uniform thickness.

In one embodiment, the LPPS system 300 performs a PSTF process to form the second protective layer 313 having a thickness of 10-100 microns. PSTF refers to a process with powder feedstock where deposition is predominantly by molten droplets, similar to conventional plasma spray but at greatly reduced chamber pressures. For PSTF processes, a pressure of around 0.1-50 mbar may be used to produce thin dense coatings from liquid splats using a classical thermal spray approach but at high velocity and enthalpy. PSTF processes are performed by spraying particles at high velocities (e.g., 400-800 meters per second (m/s) and high enthalpy (e.g., 8000-15,000 kJ/kg). The ceramic coatings produced by PSTF have a uniform thickness with minimal internal stresses.

In one embodiment, the LPPS system 300 performs a PSCVD process to form the second protective layer 313 having a thickness of approximately 1 to 50 microns. PSCVD refers to a plasma spray process in which an extremely low pressure of less than 1 mbar (e.g., around 0.3-1.0 mbar) and a relatively low power of less than 10 kW are used to produce thin dense coatings having a thickness of less than 50 microns. The feedstock for PSCVD processes is liquid or gaseous precursors. The ceramic coatings produced by PSCVD have a uniform thickness.

FIG. 5 illustrates one embodiment of a process for forming multiple plasma sprayed protective layers over a chamber component. At block 502, an LPPS or APPS process is selected for plasma spraying a first plasma resistant layer. At block 504, an article (e.g., a substrate) is prepared for coating. The article may be a metal substrate such as aluminum, copper, magnesium, or another metal or a metal alloy. The article may also be a ceramic substrate, such as alumina, yttria, or another ceramic or a mixture of ceramics. Preparing the article may include shaping the article to a desired form, grinding, blasting or polishing the article to provide a particular surface roughness and/or cleaning the article. In one embodiment, the article is roughened. In another embodiment, the article is not roughened prior to depositing the ceramic coating.

At block 506, an article is placed into an APPS system or into a vacuum chamber of an LPPS system depending on an outcome at block 502. At block 508, optimal powder characteristics for plasma spraying a ceramic coating using an LPPS or APPS process are selected. In one embodiment, an optimized agglomerate powder size distribution is selected where 10% of agglomerate powder (D10) has a size of less than 10 μm, 50% of agglomerate powder (D50) has a size of 20-30 μm and 90% of agglomerate powder (D90) has a size of less than 55 μm.

Raw ceramic powders having specified compositions, purity and particle sizes are selected. The ceramic powder may be formed of any of the rare earth oxides previously discussed. The raw ceramic powders are then mixed. These raw ceramic powders may have a purity of 99.9% or greater in one embodiment. The raw ceramic powders may be mixed using, for example, ball milling. The raw ceramic powders may have a powder size in a range of between about 100 nm-20 μm. In one embodiment, the raw ceramic powders have a powder size of approximately 5 μm.

After the ceramic powders are mixed, they may be calcinated at a specified calcination time and temperature. In one embodiment, a calcination temperature of approximately 1200-2000° C. (e.g., 1400° C. in one embodiment) and a calcination time of approximately 2-5 hours (e.g., 3 hours in one embodiment) is used. The spray dried granular particle size for the mixed powder may have a size distribution of approximately 30 μm in one embodiment.

At block 510, optimal plasma spray parameters for plasma spraying a ceramic coating using an LPPS or APPS process are selected. The parameters may be adjusted to values falling within the ranges shown in Table 3 based on a subsequent plasma spray process to be performed. In one embodiment, optimizing plasma spray parameters includes, but is not limited to, setting a plasma gun power, chamber pressure and a composition of spray carrier gas. Optimizing the powder characteristics and the plasma spray parameters may lead to a coating with a decreased porosity and an increased density and an increased percentage of fully melted nodules. Such a decreased porosity and increased density improves protection of a coated article from corrosive elements such as plasmas. Also, fully melted nodules are less likely to break free of the ceramic coating and contaminate the wafer causing particle problems. In one embodiment, an optimal powder type and an optimal powder size distribution are selected for the powder.

At block 512, the article is coated according to the selected powder characteristics and plasma spray parameters to form a first plasma resistant layer. LPPS and APPS processes may melt materials (e.g., ceramic powders) and spray the melted materials onto the article using the selected parameters. The first plasma resistant layer may have a thickness of about 20-500 microns, and a thickness of about 100-200 microns in a particular embodiment. Additionally, the first plasma resistant layer may have a porosity of 1-5%. In some instances, the first plasma resistant layer has a porosity of around 3-5%.

The plasma spray process may be performed in multiple spray passes. For each pass, the angle of a plasma spray nozzle may change to maintain a relative angle to a surface that is being sprayed. For example, the plasma spray nozzle may be rotated to maintain an angle of approximately 45 degrees to approximately 90 degrees with the surface of the article being sprayed. Each pass may deposit a thickness of up to approximately 25 μm, depending on the plasma spray process that is being performed and the input parameters. The first plasma resistant layer may have a surface roughness of about 100-300 micro-inches.

At block 514, a PSTF, PSCVD or PSPVD process is selected for forming a second plasma resistant layer. At block 516, a determination may be made as to whether the first plasma resistant layer was formed using LPPS or APPS. If APPS was used for the first plasma resistant layer, then the process continues to block 518, and the article is loaded into a vacuum chamber of an LPPS system. Otherwise the process proceeds to block 520, and the PSTF, PSCVD or PSPVD process may be performed following the LPPS process.

At block 520, the plasma spray parameters are adjusted or selected and/or the powder parameters are adjusted or selected to optimize deposition using the PSTF, PSCVD or PSPVD process. For example, if PSTF is to be performed, the pressure may be reduced to approximately 0.1-50.0 Mbar. If PSPVD is to be performed, the pressure may be reduced to approximately 0.1-50.0 Mbar, and the plasma power may be unchanged or increased. If PSCVD is to be performed, a liquid or vapor is supplied, pressure may be reduced to less than about 0.4 Mbar, and plasma power is reduced to less than about 10 kW. The parameters may be adjusted to values falling within the ranges shown in Table 3 based on a subsequent plasma spray process to be performed. For example, if an additional plasma resistant layer is to be deposited using PSTF, then the plasma spray parameters would be adjusted to within the ranges shown for PSTF.

At block 522, the article is plasma sprayed using a PSTF, PSPVD or PSCVD process to form a second plasma resistant layer. PSCVD, PSPVD and/or PSTF processes may melt or vaporize materials (e.g., ceramic powders, or liquid or gaseous precursors) and spray the melted or vaporized materials onto the article using the selected parameters. The second plasma resistant layer may have a thickness of less than about 100 microns. In one embodiment, the second plasma resistant layer has a thickness of approximately 10 microns or less. The second plasma resistant layer may be conformal, uniform, and denser than the first plasma resistant layer. In one embodiment, the second plasma resistant layer has a porosity of less than 1%.

At block 524, it is determined whether to deposit any additional layers for the plasma resistant ceramic coating. If an additional layer is to be deposited, the process may return to block 514 for plasma spraying another layer using a PSCVD, PSPVD or PSTF process. Alternatively, the process may return to block 502, 506 or 508 for plasma spraying another layer using an APPS or LPPS process. Otherwise the method ends.

TABLE 1 Plasma Spray Input Parameters LPPS PSPVD PSTF APPS PSCVD Input Parameter Unit Range Range Range Range Range Power of Plasma kW  9-300  9-300  9-300  9-300 <100 Gun Current A 300-1000 300-1000 300-1000 300-1000 <1000 Gun Voltage V 30-300 30-300 30-300 30-300 <100 Powder Feed g/min.  5-200  5-200  5-200  5-200  5-200 Distance mm 500-3000 500-3000 500-3000 50-200 500-3000 Gas Flow Rate L/min. 30-500 30-500 30-500 30-500 30-500 Pressure Mbar 10-100 0.1-50   0.1-50   1013 0.1-50  

Table 1 illustrates input parameters that may be used for coating the article using an LPPS process, a PSPVD process, a PSTF process, an APPS process, or a PSCVD process. The parameters include, but are not limited to, power of plasma, gun current, gun voltage, powder feed rate, gun stand-off distance, gas flow rate and chamber pressure.

FIGS. 6-7 illustrate cross sectional side views of articles (e.g., chamber components) covered by plasma resistant ceramic coatings including two or more protective layers. Referring to FIG. 6, a body 605 of the article 600 includes a plasma resistant ceramic coating 606 having a first thick film protective layer 608 and a second thin film protective layer 610. In one embodiment, the first thick film protective layer 608 is a plasma-sprayed layer having a thickness of about 20-500 μm and a porosity of about 1-5%. In one embodiment, the thin film protective layer is a plasma-sprayed layer having a thickness of about 1-100 μm and a porosity of less than 1%. In one embodiment, the thick film protective layer is deposited by LPPS and the thin film protective layer is deposited by PSTF, PSCVD or PSPVD. In one embodiment, the thick film protective layer is deposited by APPS, and the thin film protective layer is deposited by one of PSTF, PSPVD or PSCVD.

Examples of ceramics that may be used to form the first thick film protective layer 608 and thin film protective layer 610 include Y₃Al₅O₁₂, Y₄Al₂O₉, Er₂O₃, Gd₂O₃, Er₃Al₅O₁₂, Gd₃Al₅O₁₂, a ceramic compound comprising Y₄Al₂O₉ and a solid-solution of Y₂O₃—ZrO₂ (Y₂O₃—ZrO₂ solid solution), or any of the other ceramic materials previously identified. Other Er based and/or Gd based plasma resistant rare earth oxides may also be used to form the thick film protective layer 608 and thin film protective layer 610. In one embodiment, the same ceramic material is not used for two adjacent thin film protective layers. However, in another embodiment adjacent layers may be composed of the same ceramic.

FIG. 7 illustrates a cross sectional side view of another embodiment of an article 700 having a plasma resistant ceramic coating 706 that includes a stack of protective layers deposited over a body 705 of the article 700. Article 700 is similar to article 700, except that plasma resistant ceramic coating 706 has four protective layers 708, 710, 715, 718. As shown, the protective layers may be alternating thick film protective layers and thin film protective layers. Alternatively, multiple thick film protective layers may be deposited followed by a final thin film protective layer. Thick film protective layers may be deposited by LPPS or APPS and have a thickness of 20-500 microns. Thin film protective layers may be deposited by PSTF, PSPVD or PSCVD and have a thickness of 1-100 microns. The plasma resistant ceramic coating 706 may have any number of protective layers.

In one embodiment, the bottom protective layers 608, 708 include a coloring agent that will cause the deposited protective layer to have a particular color. Examples of coloring agents that may be used include Nd₂O₃, Sm₂O₃ and Er₂O₃. Other coloring agents may also be used. Accordingly, when the second protective layer 610, 710 wears away, an operator may have a visual queue that it is time to refurbish or exchange the article 600, 700.

The preceding description sets forth numerous specific details such as examples of specific systems, components, methods, and so forth, in order to provide a good understanding of several embodiments of the present disclosure. It will be apparent to one skilled in the art, however, that at least some embodiments of the present disclosure may be practiced without these specific details. In other instances, well-known components or methods are not described in detail or are presented in simple block diagram format in order to avoid unnecessarily obscuring the present disclosure. Thus, the specific details set forth are merely exemplary. Particular implementations may vary from these exemplary details and still be contemplated to be within the scope of the present disclosure.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrase “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. In addition, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.”

Although the operations of the methods herein are shown and described in a particular order, the order of the operations of each method may be altered so that certain operations may be performed in an inverse order or so that certain operation may be performed, at least in part, concurrently with other operations. In another embodiment, instructions or sub-operations of distinct operations may be in an intermittent and/or alternating manner.

It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. The scope of the disclosure should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. 

What is claimed is:
 1. A method of plasma spraying an article comprising: inserting the article into a vacuum chamber for a low pressure plasma spraying system; performing a low pressure plasma spray (LPPS) process by the low pressure plasma spraying system to form a first plasma resistant ceramic layer on the article, the first plasma resistant ceramic layer having a thickness of 20-500 microns and a porosity of over 1%; and performing a plasma spray chemical vapor deposition (PSCVD) process by the low pressure plasma spraying system to deposit a second plasma resistant ceramic layer on the first plasma resistant ceramic layer, the second plasma resistant ceramic layer having a thickness of approximately 1-50 microns and a porosity of less than 1%.
 2. The method of claim 1, wherein the first plasma resistant ceramic layer and the second plasma resistant ceramic layer each comprise at least one of Y₃Al₅O₁₂, Y₄Al₂O₉, Er₂O₃, Gd₂O₃, Y₂O₃, Er₃Al₅O₁₂, Gd₃Al₅O₁₂, YF₃, Nd₂O₃, or a ceramic compound comprising Y₄Al₂O₉ and a solid-solution of Y₂O₃—ZrO.
 3. The method of claim 1, wherein the first plasma resistant ceramic layer consists of a rare earth oxide and the second plasma resistant ceramic layer consists of the rare earth oxide.
 4. The method of claim 1, wherein the first plasma resistant ceramic layer comprises a coloring agent.
 5. The method of claim 1, wherein the article is a chamber component comprising at least one of a metal or a sintered ceramic.
 6. The method of claim 1, wherein a first set of plasma spray parameters are used while performing the LPPS process and a second set of plasma spray parameters are used while performing the PSCVD process.
 7. The method of claim 1, wherein the LPPS process and the PSCVD process are performed in the vacuum chamber as part of a single plasma spray recipe.
 8. The method of claim 1, wherein: performing the LPPS process comprises reducing a pressure of the vacuum chamber to about 20-200 mbar and injecting a powder feedstock into a plasma jet; and performing the PSCVD process comprises reducing the pressure of the vacuum chamber to about 0.1-1.0 mbar, setting a power of the low pressure plasma spraying system to less than about 10 kW, and injecting a liquid feedstock or a vapor feedstock into the plasma jet.
 9. The method of claim 1, wherein at least one of the first plasma resistant ceramic layer or the second plasma resistant ceramic layer comprises Y₂O₃ in a range of 40-60 mol %, ZrO₂ in a range of 32-50 mol %, and Al₂O₃ in a range of 10-20 mol %.
 10. The method of claim 1, wherein at least one of the first plasma resistant ceramic layer or the second plasma resistant ceramic layer comprises Y₂O₃ in a range of 40-49 mol %, ZrO₂ in a range of 20-40 mol %, and Al₂O₃ in a range of 20-40 mol %.
 11. The method of claim 1, wherein at least one of the first plasma resistant ceramic layer or the second plasma resistant ceramic layer comprises Y₂O₃ in a range of 76-90 mol %, ZrO₂ in a range of 1-20 mol %, and Al₂O₃ in a range of 10-20 mol %.
 12. The method of claim 1, wherein at least one of the first plasma resistant ceramic layer or the second plasma resistant ceramic layer comprises Y₂O₃ in a range of 76-90 mol %, ZrO₂ in a range of 1-20 mol %, and Al₂O₃ in a range of 10-20 mol %.
 13. The method of claim 1, wherein at least one of the first plasma resistant ceramic layer or the second plasma resistant ceramic layer comprises Y₂O₃ in a range of 40-60 mol %, ZrO₂ in a range of 1-20 mol %, and Al₂O₃ in a range of 31-40 mol %.
 14. The method of claim 1, wherein at least one of the first plasma resistant ceramic layer or the second plasma resistant ceramic layer comprises Y₂O₃ in a range of 40-45 mol %, ZrO₂ in a range of 0-10 mol %, Er₂O₃ in a range of 35-40 mol %, Gd₂O₃ in a range of 5-10 mol %, and SiO₂ in a range of 5-15 mol %.
 15. The method of claim 1, wherein the first plasma resistant ceramic layer consists essentially of a first ceramic selected from a group consisting of Y₄Al₂O₉, Er₂O₃, Er₃Al₅O₁₂ or Gd₃Al₅O₁₂ and the second plasma resistant ceramic layer consists essentially of the first ceramic or a second ceramic selected from the group consisting of Y₃Al₅O₁₂, Y₄Al₂O₉, Er₂O₃, Gd₂O₃, Y₂O₃, Er₃Al₅O₁₂, Gd₃Al₅O₁₂, YF₃, Nd₂O₃, or a ceramic compound comprising Y, Al, O and Zr.
 16. The method of claim 1, wherein the first plasma resistant ceramic layer and the second plasma resistant ceramic layer each consists essentially of Y₃Al₅O₁₂ or Y₄Al₂O₉.
 17. The method of claim 1, wherein the first plasma resistant ceramic layer and the second plasma resistant ceramic layer each consists essentially of Er₂O₃.
 18. The method of claim 1, wherein the first plasma resistant ceramic layer and the second plasma resistant ceramic layer each consists essentially of a ceramic compound consisting of Y₄Al₂O₉ and a solid-solution of Y₂O₃—ZrO₂.
 19. A method of plasma spraying an article comprising: inserting the article into a vacuum chamber for a low pressure plasma spraying system; performing a low pressure plasma spray (LPPS) process by the low pressure plasma spraying system to form a first plasma resistant ceramic layer on the article, the first plasma resistant ceramic layer having a thickness of 20-500 microns and a porosity of over 1%; and performing a plasma spray physical vapor deposition (PSPVD) process by the low pressure plasma spraying system to deposit a second plasma resistant ceramic layer on the first plasma resistant ceramic layer, the second plasma resistant ceramic layer having a thickness of about 10-100 microns and a porosity of less than 1%.
 20. The method of claim 19, wherein performing the LPPS process comprises feeding a powder having a particular composition into a plasma jet, and wherein performing the PSPVD process comprises feeding the powder having the particular composition into the plasma jet. 